1. Field of the Invention
The present invention relates to a plasma processing apparatus.
2. Description of Related Art
For example, as disclosed in JP 4074370 B, there is a known vapor deposition apparatus using a plasma assisted method in which plasma is formed to accelerate vapor deposition. The plasma can accelerate a chemical reaction of a vapor deposition material of a vapor deposition film. However, when the plasma comes in contact with a vapor deposition target body in which the vapor deposition film is formed on its surface, a phenomenon called a bombardment effect is caused so that the material on the surface of the vapor deposition target body is bombarded. In order to clean the surface of the vapor deposition target body (processing target), the bombardment effect with the plasma is positively used in some cases.
A plasma gun which emits electrons with a plasma gas to form the plasma has a convergent coil for forming a magnetic flux to guide the emitted electrons in an axis direction in general. The magnetic flux formed by the convergent coil extends from an outlet side of the convergent coil in an axis direction, turns over outwardly, and returns to an inlet side of the convergent coil. The magnetic flux which turns over outwardly could partially penetrate the vapor deposition target body or pass through a vicinity of the vapor deposition target body. Since the plasma moves along with the magnetic flux, in the conventional vapor deposition apparatus, the plasma is slightly guided to the vicinity of the vapor deposition target body. Therefore, in the conventional vapor deposition apparatus, it is difficult to completely separate the vapor deposition target body from the plasma, and the plasma could damage the surface of the vapor deposition target body due to the bombardment effect.
JP 4-329637 A discloses the invention in which, in an ion sputtering apparatus for coating a processing target with a material sputtered by plasma gas, a pair of coils for forming a repelling magnetic flux across the processing target is provided, and a positional relationship between a cusp surface on which the magnetic flux of both coils are canceled and the processing target is adjusted to control a speed of ion sputtering (bombardment). According to this invention, the plasma is guided toward the processing target basically, so that the strength of the sputtering can be adjusted, but it is impossible to separate the processing target from the plasma and completely prevent the sputtering.